Method of making a patterned magnetic recording head

ABSTRACT

A thin film magnetic recording head utilizing a timing based servo pattern is fabricated using a focused ion beam (FIB). The recording head is fabricated by sputtering a magnetically permeable thin film onto a substrate. A gap pattern, preferably a timing based pattern, is defined on the thin film and the FIB cuts a gap through the thin film based on that pattern. Once completed, the recording head is used to write a servo track onto magnetic tape. The timing based servo track then allows for the precise alignment of data read heads based on the positional information obtained by a servo read head which scans the continuously variable servo track.

FIELD OF THE INVENTION

[0001] This invention relates generally to magnetic recording heads andmore particularly to a method of making thin-film magnetic heads forimprinting time based servo patterns on a magnetic media.

BACKGROUND OF THE INVENTION

[0002] While a variety of data storage mediums are available, magnetictape remains a preferred forum for economically storing large amounts ofdata. In order to facilitate the efficient use of this media, magnetictape will have a plurality of data tracks extending in a transducingdirection of the tape. Once data is recorded onto the tape, one or moredata read heads will read the data from those tracks as the tapeadvances, in the transducing direction, over the read head. It isgenerally not feasible to provide a separate read head for each datatrack, therefore, the read head(s) must move across the width of thetape (in a translating direction), and center themselves over individualdata tracks. This translational movement must occur rapidly andaccurately.

[0003] In order to facilitate the controlled movement of a read headacross the width of the media, a servo control system is generallyimplemented. The servo control system consists of a dedicated servotrack embedded in the magnetic media and a corresponding servo read headwhich correlates the movement of the data read heads.

[0004] The servo track contains data, which when read by the servo readhead is indicative of the relative position of the servo read head withrespect to the magnetic media in a translating direction. In one type oftraditional arrangement, the servo track was divided in half. Data wasrecorded in each half track, at different frequencies. The servo readhead was approximately as wide as the width of a single half track.Therefore, the servo read head could determine its relative position bymoving in a translating direction across the two half tracks. Therelative strength of a particular frequency of data would indicate howmuch of the servo read head was located within that particular halftrack.

[0005] While the half track servo system is operable, it is bettersuited to magnetic media where there is no contact between the storagemedium and the read head. In the case of magnetic tape, the tapeactually contacts the head as it moves in a transducing direction. Boththe tape and the head will deteriorate as a result of this frictionalengagement; thus producing a relatively dirty environment. As such,debris will tend to accumulate on the read head which in turn causes thehead to wear even more rapidly. Both the presence of debris and thewearing of the head have a tendency to reduce the efficiency andaccuracy of the half track servo system.

[0006] Recently, a new type of servo control system was created whichallows for a more reliable positional determination by reducing thesignal error traditionally generated by debris accumulation and headwear. U.S. Pat. No. 5,689,384, issued to Albrect et al. on Nov. 19,1997, introduces the concept of a timing based servo pattern, and isherein incorporated by reference in its entirety.

[0007] In a timing based servo pattern, magnetic marks (transitions) arerecorded in pairs within the servo track. Each mark of the pair will beangularly offset from the other. Virtually any pattern, other thanparallel marks, could be used. For example, a diamond pattern has beensuggested and employed with great success. The diamond will extendacross the servo track in the translating direction. As the tapeadvances, the servo read head will detect a signal or pulse generated bythe first edge of the first mark. Then, as the head passes over thesecond edge of the first mark, a signal of opposite polarity will begenerated. Now, as the tape progresses no signal is generated until thefirst edge of the second mark is reached. Once again, as the head passesthe second edge of the second mark, a pulse of opposite polarity will begenerated. This pattern is repeated indefinitely along the length of theservo track. Therefore, after the head has passed the second edge of thesecond mark, it will eventually arrive at another pair of marks. At thispoint, the time it took to move from the first mark to the second markis recorded. Additionally, the time it took to move from the first mark(of the first pair) to the first mark of the second pair is similarlyrecorded.

[0008] By comparing these two time components, a ratio is determined.This ratio will be indicative of the position of the read head withinthe servo track, in the translating direction. As the read head moves inthe translating direction, this ratio will vary continuously because ofthe angular offset of the marks. It should be noted that the servo readhead is relatively small compared to the width of the servo track.Ideally, the servo head will also be smaller than one half the width ofa data track. Because position is determined by analyzing a ratio of twotime/distance measurements, taken relatively close together, the systemis able to provide accurate positional data, independent of the speed(or variance in speed) of the media.

[0009] By providing more than one pair of marks in each grouping, thesystem can further reduce the chance of error. As the servo read headscans the grouping, a known number of marks should be encountered. Ifthat number is not detected, the system knows an error has occurred andvarious corrective measures may be employed.

[0010] Of course, once the position of the servo read head is accuratelydetermined, the position of the various data read heads can becontrolled and adjusted with a similar degree of accuracy.

[0011] When producing magnetic tape (or any other magnetic media) theservo track is generally written by the manufacturer. This results in amore consistent and continuous servo track, over time. To write thetiming based servo track described above, a magnetic recording headbearing the particular angular pattern as its gap structure, must beutilized. As it is advantageous to minimize the amount of tape that isdedicated to servo tracks, to allow for increased data storage, and itis necessary to write a very accurate pattern, a very small and veryprecise servo recording head must be fabricated.

[0012] Historically, servo recording heads having a timing based patternhave been created utilizing known plating and photolithographictechniques. A head substrate is created to form the base of therecording head. Then, a pattern of photoresist is deposited onto thatsubstrate. The photoresist pattern essentially forms the gap in thehead. Therefore, the pattern will replicate the eventual timing basedpattern. After the pattern has been applied a magnetically permeablematerial such as NiFe is plated around the photoresist pattern. Once soformed, the photoresist is washed away leaving a head having a thin filmmagnetic substrate with a predefined recording gap.

[0013] Alternatively, the ion milling is used to form a first layerhaving a relatively large gap. A pattern of photoresist is applied in aninverse of the above described pattern. That is, photoresist is appliedeverywhere except where the timing based pattern (gap) is to be formed.Ion milling is used to cut the gap through the first layer. Then anadditional layer of the magnetically permeable material is deposited byplating over the first layer and a narrow gap is formed into this layerby the above described photolithographic process. This approach producesa more efficient head by creating a thicker magnetic pole system.

[0014] While the above techniques are useful in producing timing basedrecording heads, they also limit the design characteristics of the finalproduct. In the first method, only materials which may be plated can beutilized, such as NiFe (Permalloy). Generally, these materials do notproduce heads which have a high wear tolerance. As such, these headswill tend to wear out in a relatively short time. In addition, thisclass of materials have a low magnetic moment density (10 kGauss forNiFe), or saturation flux density, which limits their ability to recordon very high coercivity media.

[0015] The second method also relies on plating for the top magneticlayer and is therefore limited to the same class of materials. Inaddition, the use of ion milling makes the fabrication of such a headoverly complex. The photoresist pattern can be applied relativelyprecisely; thereby forming a channel over the gap. However, thetraditional ion milling technique is rather imprecise and as the ionspass through that channel they are continuously being deflected.Conceptually, in any recording gap, so cut, the relative aspect ratiosinvolved prevent a precise gap from being defined. In other words, thisis a shadowing effect created by the photoresist and causes the gap inthe magnetically permeable material to be angled. Generally, thesidewalls of the gap will range between 45°-60°from horizontal. Thisintroduces a variance into the magnetic flux as it exits the gap,resulting in a less precise timing based pattern being recorded onto theservo track.

[0016] Therefore, there exists a need to provide a magnetic recordinghead capable of producing a precise timing based pattern. Furthermore,it would be advantageous to produce such a head having a tape bearingsurface which is magnetically efficient as well as wear resistant andhence a choice of sputtered rather than plated materials are required.Thus, it is proposed to use a fully dry process to fabricate a timebased head using predominantly iron nitride based alloys.

SUMMARY OF THE INVENTION

[0017] The present invention relates to a method of fabricating amagnetic recording head, and more particularly a recording head forproducing a time based servo pattern.

[0018] A substrate consisting of a ceramic member, glass bonded betweena pair of ferrite blocks is prepared. The substrate is then cleaned,polished and if desired, ground to a particular curvature. On top ofthis substrate, a magnetically permeable thin film is deposited,preferably by a sputtering process. The thin film is selected from aclass of materials having a high wear tolerance as well as a highmagnetic moment density, such as FeN. The alloys in this class ofmaterials need to be sputtered onto the substrate, as other thin filmdeposition techniques, such as plating, are incompatible with thesematerials.

[0019] Once the thin film is present, the substrate is placed within thepath of a focused ion beam (FIB) orthogonally oriented to the majorsurface of the thin film. The FIB is used to mill a complex patternedgap though the thin film layer. This gap is extremely precise and willallow the recording head to accurately produce a similar pattern onmagnetic tape.

[0020] The FIB must be controlled to only mill the patterned gap and noother portion of the thin film. To define these parameters within theFIB control system, several techniques are available. In general, anon-destructive pattern is applied to the surface of the thin film. Agraphical interface within the FIB control system allows the operator tovisually align the pattern with the FIB milling path. One way toaccomplish this is to apply a very thin layer of photoresist to the thinfilm. A mask is then employed to create the very precise gap pattern.Because photoresist is visually distinct from the remainder of thesubstrate, the FIB can be aligned with this pattern. As opposed to theusual thick film photoresist used in traditional ion milling as aprotective layer (or selectively etched layer), the photoresist in thepresent invention will serve no other purpose in the milling process.Alternatively, numerical coordinates, representing the gap to be cut,can be directly entered into the FIB control system.

[0021] Once the gap or gaps have been cut into the thin film, thesubstrate is coupled with a coil to produce a functional recording head.

[0022] It is an object of the present invention to provide a method ofmaking a magnetic recording head having a precisely defined gapstructure.

[0023] It is another object of the present invention to produce amagnetic recording head utilizing a focused ion beam to define the gapand track width structure.

[0024] It is still another object of the present invention tosimultaneously define and create all three dimensions of a gap structurein a magnetic head.

[0025] It is yet still another object of the present invention tofabricate a magnetic recording head wherein the gap depth is determinedprimarily by the thickness of the deposited thin film.

[0026] It is yet another object of the invention to use a focused ionbeam to produce a thin film magnetic recording head employing a timingbased servo pattern.

[0027] It is yet still another object of the present invention toproduce a thin film magnetic recording head having a highly wearresistant tape bearing surface.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a side planar view of a substrate bearing a magneticthin film.

[0029]FIG. 2 is a top planar view of the substrate shown in FIG. 1.

[0030]FIG. 3 is top planar view of a portion of thin film, bearingindicia of a gap to be milled.

[0031]FIG. 4 is a schematic diagram of a FIB milling a gap into a thinfilm.

[0032]FIG. 5 is a top planar view of a thin film having gaps milled by aFIB.

[0033]FIG. 6 is a side sectional view taken about line VI-VI.

[0034]FIG. 7 is a top planar view of a thin film having gaps milled by aFIB.

[0035]FIG. 8 is side sectional view taken about line VII-VII.

[0036]FIG. 9 is a top planar view of a portion of thin film having a gapand endpoints milled by a FIB.

[0037]FIG. 10 is a top planar view of a substrate bearing gaps and airbleed slots.

[0038]FIG. 11 is an end planar view of a substrate bearing air bleedslots.

[0039]FIG. 12 is a side planar view of a magnetic recording head.

[0040]FIG. 13 is an end planar view of a magnetic recording head.

[0041]FIG. 14 is a partial perspective view of thin film layer bearing aset of time based or angled recording gap pairs.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0042] The present invention is a method of making a thin film magneticrecording head using a focused ion beam (FIB) to mill out gaps in thetape bearing surface. Referring to FIG. 1, a substrate 10 is created byglass bonding two C-shaped ferrite blocks 12 to a medially disposedceramic member 14. The sizes and relative proportions of the ferriteblocks 12 and ceramic member 14 may vary as dictated by the desiredparameters of the completed recording head. Furthermore, the choice ofmaterials may also vary so long as blocks 12 remain magnetic whilemember 14 remains magnetically impermeable.

[0043] A layer of magnetically permeable material is deposited as a thinfilm 16 across an upper surface of each of the ferrite blocks 12, aswell as the upper surface of the ceramic member 14. The magneticallypermeable thin film 16 will become the tape bearing and data writingsurface for the magnetic head 5 (see FIGS. 12 & 13). As such, it isdesirable to form the layer of thin film 16 from a material which has arelatively high magnetic moment density (greater or equal to about 15kGauss) and is also wear resistant. An exemplary material for thispurpose is FeN or alternatively Sendust™. For example, FeN has amagnetic moment density on the order of 19 to 20 kGauss and is resistantto the frictional deterioration caused by continuous tape engagement.Any of the alloys in the iron nitride family, such as iron aluminumnitride, iron tantalum nitride, etc., and including any number ofelements, are also ideally suited. FeXN denotes the members of thisfamily, wherein X is a single element or a combination of elements, asis known in the art.

[0044] FeXN is created by sputtering a FeX alloy (or simply Fe) in anitrogen rich environment. It is not available in quantities sufficientfor plating. Furthermore, even if so available, the FeXN would decomposeduring the electrolytic plating process. This is in stark contrast tothe simple alloys which may be readily utilized in electrolytic platingtechniques. Therefore, while it is advantageous to use alloys, such asFeXN, magnetic recording heads cannot be formed with them, in anypreviously known plating process. In addition, the most desirable alloysto use are often composed of three of more elements. Plating isgenerally limited to the so called binary alloys, and as explained aboveis not conducive to binary gaseous alloys, such as FeN. The use ofsputtering in combination with the use of a FIB, not only allows any ofthese materials to be used but also produces a better wearing magneticthin film with a higher saturation flux density and of sufficientpermeability for use as a servo write head.

[0045] Referring again to FIG. 1, the thin film 16 is sputtered onto thesurface of the ferrite blocks 12 and the ceramic member 14. Prior to thesputtering process, the surface is polished and prepared in a mannerknown to those skilled in the art. If desired, the surface may be groundto produce a slight curvature. This curvature will facilitate smoothcontact between the tape and the completed head 5 as the tape movesacross the tape bearing surface.

[0046] The thickness of the deposited thin film 16 determines theefficiency of the magnetic head and also its predicted wear life. Thethicker the tape bearing surface (thin film 16) is, the longer the headwill last. Conversely, the thicker the magnetic film, the longer it willtake to process or etch with a FIB and it will also process lessprecisely. Therefore, the thin film should be deposited in a thicknessof about 1 to 5 μm. Ideally, the thickness will be about 2 to 3 μm.

[0047]FIG. 2 is a top view of the substrate 10 and in particular themajor surface of magnetic thin film 16 with the underlying ceramicmember 14 shown in dashed lines. The area 18 is defined by the uppersurface of the ceramic member 14 (the magnetic sub-gap) and is where theappropriate gaps will eventually be milled.

[0048] Referring to FIG. 3, only area 18 is shown. Within area 18, someindicia 20 of the eventual gap positions are laid down. It should benoted that two diamond shaped gaps are to be milled as shown in FIG. 3;however any shape and any number of gaps could be created. Indicia 20 issimply an indication of where the FIB is to mill. One way ofaccomplishing this is to place a layer of photoresist 22 down and definethe indicia 20 with a mask. Using the known techniques ofphotolithography, a layer of photoresist 22 will remain in all of area18 except in the thin diamond defined by indicia 20. Alternatively, thephotoresist area could be substantially smaller than area 18, so long asit is sufficient to define indicia 20. The photoresist differs in colorand height from the thin film 16 and therefore produces the visuallydiscernible pattern. This pattern is then registered with the FIBcontrol system through a graphical interface; thus delineating where theFIB is to mill. The photoresist serves no other purpose, in thisprocess, than to visually identify a pattern. As such, many alternativesare available. Any high resolution printing technique capable of marking(without abrading) the surface of the thin film 16 could be used.Alternatively, the pattern could be created completely within the FIBcontrol system. That is, numerical coordinates controlling the path ofthe FIB and representing the pattern could be entered; thus, obviatingthe need for any visual indicia to be placed onto the magnetic thin film16. Finally, a visual pattern could be superimposed optically onto theFIB graphical image of the substrate 10, thereby producing a visuallydefinable region to mill without actually imprinting any indicia ontothe substrate 10.

[0049] In any of the above described ways, the FIB 24 is programmed totrace a predefined pattern, such as the diamond indicia 20 shown in FIG.3. The FIB will be orientated in a plane orthogonal to the major surfaceof the thin film 16.

[0050]FIG. 4 is a sectional view of FIG. 3, taken about line IV-IV andillustrates the milling process utilizing FIB 24. The upper surface ofthe thin film 16 has been coated with a thin layer of photoresist 22.The visual indicia 20 of the diamond pattern is present, due to the areaof that indicia 20 being void of photoresist. The FIB 24 has alreadymilled a portion of the pattern forming gap 30. The FIB as shown hasjust begun to mill the right half of the pattern. The beam of ions 26 isprecisely controlled by the predefined pattern which has been enteredinto the FIB's control system. As such, the beam 26 will raster back andforth within the area indicated by indicia 20. The beam 26 willgenerally not contact a significant amount of the photoresist 22 andwill create a gap 30 having vertical or nearly vertical side walls. Thewidth of the ion beam is controllable and could be set to leave apredefined amount of space between the edge of the side wall and theedge of the indicia 20. The FIB 24 will raster back and forth until allof the indicia 20 have been milled for that particular head.

[0051] After the FIB 24 has milled all of the gap(s) 30, the photoresist22 is washed away. Alternatively, any other indicia used would likewisebe removed. FIG. 5 illustrates area 18 of substrate 10 after the photoresist 22 has been removed. Thin film 16 is exposed and has preciselydefined gaps 30 milled through its entire depth, down to the ceramicmember 14. FIG. 6 is a sectional view of FIG. 5 taken about line VI-VIof FIG. 5 and illustrates the milled surface of gap 30. The gap 30 isprecisely defined, having vertical or nearly vertical walls.

[0052] Referring to FIG. 14, a partial perspective view of a time basedrecording head 5 is shown. The major surface 50 of thin film 16 lies ina plane defined by width W, length L, and depth D. D is the depositedthickness of the magnetic film 16. The FIB will always mill through thinfilm 16 through a plane perpendicular to the major surface 50 whichwould also be parallel to depth D. By conventional standards, the gap 30will have a magnetic gap depth equal to depth D and a gap width equal towidth W and a gap length (L′)equal to the span of gap 30.

[0053] The upper surface of thin film 16, shown in FIG. 7, representsone of many alternative time based patterns which may be created using aFIB 24. Here, gaps 30 will be milled in exactly the same fashion asdescribed above, except that indicia 20, when utilized, would haveformed the pattern shown in FIG. 7. FIG. 8 is a sectional view takenabout line VII-VII of FIG. 7 and shows how gap 30 continues to haveprecisely defined vertical sidewalls. Furthermore, the upper horizontalsurface 32 of ceramic member 14 is also precisely defined.

[0054]FIG. 9 illustrates yet another pattern which may be defined usingFIB 24. Here, gap 30 is in the shape of an augmented diamond. Ratherthan defining a diamond having connected corners, gap 30 is milled tohave termination cells or endpoints 34, 35, 36 and 37. Creatingendpoints 34, 35, 36 and 37 increases the definition of the finishedrecorded pattern near the ends of the track.

[0055] The next step in the fabrication process is to create air bleedslots 40 in the tape bearing surface of the substrate 10, as shown inFIG. 10. Once substrate 10 has been fabricated into a recording head,magnetic tape will move across its upper surface in a transducingdirection, as shown by Arrow B. Therefore, the air bleed slots 40 arecut perpendicular to the transducing direction. As the tape moves overthe recording head at relatively high speed, air entrainment occurs.That is, air is trapped between the lower surface of the tape and theupper surface of the recording head. This results from the magnetictape, comprised of magnetic particles affixed to a substrate, beingsubstantially non-planar on a microscopic level. As the tape moves overthe recording head, the first air bleed slot encountered serves to skiveoff the trapped air. The second and subsequent slots continue thiseffect, thus serving to allow the tape to closely contact the recordinghead. As the tape passes over the recording gap(s) 30, it is also heldin place by the other negative pressure slot 42,43 encountered on theopposite side of the gap(s) 30. Therefore, there is a negative pressureslot 42,43 located on each side of the recording gap(s) 30.

[0056]FIG. 11 is a side view of the substrate 10, as shown in FIG. 10.The upper surface of the substrate 10 has a slight curvature or contour.This acts in concert with the air bleed slots to help maintain contactwith the magnetic tape. The air bleed slots 40 are cut into thesubstrate 10 with a precise circular saw, as is known by those skilledin the art. The air bleed slots 40 are cut through thin film 16, whichis present but not visible in FIG. 11. Alternatively, the air bleedslots 40 could be cut prior to the thin film 16 having been deposited.

[0057] Substrate 10 has been longitudinally cut, thus removing asubstantial portion of the coupled C-shaped ferrite blocks 12 andceramic member 14. This is an optional step which results in an easierintegration of the coils and ferrite blocks. FIG. 13 illustrate how abacking block 46 is bonded to substrate 10. The backing block 46 iscomposed of ferrite or another suitable magnetic material. Wiring iswrapped about the backing block 46 thus forming an electrical coil 48.With this step, the fabrication process has been completed and amagnetic recording head 5 has been produced.

[0058] In operation, magnetic recording head 5 is secured to anappropriate head mount. Magnetic tape is caused to move over and incontact with the tape bearing surface of the head 5, which happens to bethe thin film layer 16. At the appropriate periodic interval, electricalcurrent is caused to flow through the coil 48. As a result, magneticflux is caused to flow (clockwise or counterclockwise in FIG. 13)through the back block 46, through the ferrite blocks 12, and throughthe magnetic thin film 16 (as the ceramic member 14 minimizes a directflow from one ferrite block 12 to the other causing the magnetic flux toshunt through the permeable magnetic film). As the magnetic flux travelsthrough the magnetic thin film 16, it leaks out through the patternedgaps 30, thus causing magnetic transitions to occur on the surface ofthe magnetic tape, in the same pattern and configuration as the gap 30itself.

[0059] Referring to FIGS. 10 and 12, it can be seen that the width ofthe head 5 (or substrate 10) is substantially larger than a singlepatterned gap 30. This allows the recording head to bear a plurality ofpatterned gaps 30. For example, FIG. 10 illustrate a substrate 10 havingfive recording gaps 30 which could then write five servo trackssimultaneously. More or less can be utilized as desired and the finalsize of the head 5 can be adjusted to whatever parameters are required.

[0060] Rather than cutting the substrate 10 as shown in FIG. 11 andapplying a coil as shown in FIG. 13, the substrate 10 could remain wholeand the coils could be added to the C-shaped ferrite blocks 12, as theyare shown in FIG. 1.

[0061] The above head fabrication process has been described withrespect to a magnetic recording head employing a timing based servopatter. However, the process could be applied equally well to any typeof thin film recording head. That is, those of ordinary skill in the artwill appreciate that the FIB milling of the gaps could accommodate anyshape or pattern, including the traditional single gap used inhalf-track servo tracks.

[0062] Those skilled in the art will further appreciate that the presentinvention may be embodied in other specific forms without departing fromthe spirit or central attributes thereof. In that the foregoingdescription of the present invention discloses only exemplaryembodiments thereof, it is to be understood that other variations arecontemplated as being within the scope of the present invention.Accordingly, the present invention is not limited in the particularembodiments which have been described in detail therein. Rather,reference should be made to the appended claims as indicative of thescope and content of the present invention.

I claim:
 1. A method for fabricating a magnetic recording headcomprising: providing a substrate; depositing a magnetically permeablethin film onto the substrate; defining a gap pattern; milling the gappattern with a focused ion beam.
 2. The method of claim 1 , furthercomprising coupling the substrate to a coil which controllably causesmagnetic flux to flow through the substrate and the thin film.
 3. Themethod of claim 1 , wherein providing a substrate further comprises:bonding two ferrite blocks to a ceramic member; and polishing an uppersurface of the bonded blocks and ceramic member.
 4. The method of claim3 , further comprising grinding the upper surface to produce acurvature, prior to polishing.
 5. The method of claim 1 , whereindepositing a thin film further includes sputtering a material onto thesubstrate to produce the thin film.
 6. The method of claim 5 wherein thesputtered material has a high magnetic moment density.
 7. The method ofclaim 5 wherein the sputtered material is chosen from the family of ironnitride alloys.
 8. The method of claim 5 wherein the material is FeXN.9. The method of claim 5 wherein the material is FeAlN.
 10. The methodof claim 5 wherein the material is FeTaN.
 11. The method of claim 5wherein the material is sputtered to form a thin film having a thicknessbetween 1 to 5 μm.
 12. The method of claim 1 wherein the gap patterndefined is a timing based servo pattern.
 13. The method of claim 1wherein defining a gap pattern further includes providing a visualindication of the pattern on the thin film.
 14. The method of claim 13wherein the gap pattern defined is a timing based servo pattern.
 15. Themethod of claim 13 wherein the visual indication is provided by:applying a layer of photoresist over at least a portion of the thinfilm; masking the photoresist; and removing a portion of the photoresistusing known chemical processes.
 16. The method of claim 15 wherein thegap pattern defined is a timing based servo pattern.
 17. The method ofclaim 1 wherein defining a gap pattern further includes entering thenumerical coordinates of the gap pattern into a control system of thefocused ion beam.
 18. The method of claim 17 wherein the gap patterndefined is a timing based servo pattern.
 19. The method of claim 1wherein the focused ion beam is substantially perpendicular to an uppermajor surface of the thin film during milling.
 20. The method of claim19 wherein the gap has nearly vertical side walls.
 21. The method ofclaim 1 wherein the gap has nearly vertical side walls.
 22. A magneticrecording head made by the method of claim 1 .
 23. A method offabricating a magnetic recording head for timing based servo trackscomprising: providing a magnetically permeable substrate by glassbonding two ferrite blocks to a medially disposed ceramic member;sputtering a magnetically permeable thin film onto one surface of thesubstrate thereby providing a major surface; defining a timing based gappattern; rastering a focused ion beam in a plane orthogonal to the planeof the major surface of the thin film, milling out the thin film in thedefined gap pattern; coupling the substrate to a coil which controllablycauses magnetic flux to flow through the substrate and the thin film.24. The method of claim 23 wherein the thin film is FeXN.
 25. The methodof claim 23 wherein the thin film is FeAlN.
 26. The method of claim 23wherein the thin film is FeTaN.
 27. The method of claim 23 wherein thegap pattern is defined by: depositing a layer of photoresist to at leasta portion of the thin film; masking the photoresist; removing a portionof the photoresist using photolithography.
 28. The method of claim 23wherein the gap pattern is defined by providing a visual indication ofthe pattern on the thin film.
 29. The method of claim 23 wherein thepattern is defined within a control system of the focused ion beam. 30.The method of claim 23 wherein the pattern is defined within the controlsystem by entering the numerical coordinates of the gap to be milled.31. The method of claim 23 wherein the gap has nearly vertical sidewalls.
 32. A magnetic recording head made by the method of claim 23 .